Platey-type clays include low grade "bentonites" which are found throughout the world and, depending on their field-aged condition, have varying levels of desirable physical properties. Most bentonites carry calcium as their most abundant ion. Only a few carry sodium as the dominant ion. An example of the latter is Wyoming bentonite, which is highly colloidal, plastic and swells readily in water to form thixotropic gels.
In general, smectite clays, such as bentonite, include sodium montmorillonite, and such clays have been formed by the alteration of volcanic ash in situ, but many of the clay deposits have been subjected to a geologic history less favorable than that of the Wyoming bentonites, and these lower grade clays do not possess the required physical properties of low fluid loss and higher aged viscosity, to be useful in the various applications in which high quality Wyoming bentonites are now used.
With increasing industrialization in all parts of the world, there is an increasing demand for good quality bentonite-type clays, but the cost of transporting existing supplies of high quality clay to other parts of the world is an economic obstacle. Therefore, it makes more sense to find methods of upgrading the local clay deposits.